Generic self-propelled road pavers mostly comprise an internal combustion engine such as a diesel engine, a machine frame, a chassis, running gears such as wheels or crawler tracks, a operator platform and devices for laying and paving asphalt or concrete in subbase covers or layers on the ground. In operation, asphalt which is still hot, for example, is transferred from a transport vehicle to a material bunker or bin arranged in the front of the road paver in the travelling direction and is conveyed from there via transport devices such as scraper floors through the so-called tunnel to the rear of the road paver. The asphalt is distributed from here via suitable transverse distribution apparatuses such as screw conveyors over the paving width of the so-called paving screed. The working direction designates the direction in which the road paver moves during working operation, i.e., during the paving of paving material. The known paving screeds can be provided for fixed paving widths, so-called rigid screeds, or they can be variable with respect to the paving width by means of transversely displaceable screed elements. A rigid screed is a screed device on the road paver which does not allow any variable adjustment of the paving width. The so-called basic screed, i.e., the screed which is mounted directly by respective retaining arms on the tractor of the road paver, is usually a rigid screed. A screed unit of variable working width is disclosed, for example, in DE 60 2004 009 416 T2, which discloses displaceable screeds arranged on a rigid screed as a constructional overall module. It is further known to broaden rigid screeds in sections by means of attachment screeds also having a fixed paving width. The material that is placed and distributed on the ground is compacted and smoothed by the paving screed. Compacting units are frequently provided for this purpose on the screed, e.g., a tamping beam and a smoothing screed with vibrators, which, optionally in combination with further levelling strips, produce a smooth and pre-compacted paving material layer, for example, an asphalt layer. Floating on the ground material, the paving screed is drawn behind the tractor during paving operation. Portions of the screed may be heated in order to prevent adherence of paving material. High-compaction screeds are also known, on which additional pressure bars can be provided in front of or behind the smoothing screed. Since these devices need to process the distributed paving material in a predetermined sequence, the screed has a defined orientation during operation of the road paver, and, therefore, the screed also has a working direction which corresponds to the working direction of the road paver. Such road pavers and paving screeds are known, for example, from DE 10 2013 000 788.7 of the Applicant, as well as EP 2 377 998 A2 and DE 60 2004 009 416 T2.
It frequently occurs in practice that surfacing and base layers of different widths need to be paved by one and the same road paver. The two aforementioned approaches are principally known for widening the paving screed. On the one hand, the paving width of the road paver can be increased in that further attachment segments or attachment screeds are mounted at the ends of the screed situated transversely to the working direction, via which attachments all devices of the screed, i.e., the transport device for the paving material as well as potential vibration or tamping beams, are extended. The paving width of the road paver, or the paving screed, extends in fixed steps by the width of the attachment element. The advantage of this solution is that, in terms of construction, the individual screed elements can usually be arranged in a relatively simple manner. A disadvantage, however, resides in the fact that the available paving width can only be varied by fixed intervals. If the operator wishes to cover a wide spectrum of paving widths, he will need to keep a large number attachment screeds of different widths on stock. Such road pavers are frequently used with very large paving widths, as are required for highways, for example. Obstructions can, however, occur in such construction sites, especially in the region of the side edges, which require width adjustment, for example, by means of temporary removal of an attachment screed segment. A further possibility to vary the paving width of the road paver is to provide hydraulically driven extension screeds on the lateral outer ends of the screed transversely to the working direction, which extension screeds can be retracted or extended transversely to the working direction of the road paver relative to the screed either by the driver of the road paver or by operators situated on the side of the screed. The placing width of the road paver can, for example, be varied continuously within a fixed range by means of these extension screeds which are mostly operated hydraulically, as a result of which narrowing or widening sections of a base course can be paved. The hydraulic extension screeds are also used for compensating fluctuations in the width to be paved, for example, during paving a curve of a road, and for working around potential obstructions during the paving. The advantage of these extension screeds is that it is possible to respond in a substantially more precise manner to changing paving widths. Disadvantages, however, reside in the often considerable constructive effort and the higher production and maintenance costs. Furthermore, these arrangements are frequently not suitable for large paving widths. The hydraulic extension screeds are pressurised and operated by a hydraulic pump, which is typically provided on the road paver, by means of a hydraulic fluid such as hydraulic oil. For this purpose, hydraulic lines are laid from the extension screed via the further screed parts up to the road paver, which lines connect the actuators of the extension screeds to the hydraulic system of the road paver. These hydraulic lines are connected via quick-action couplings both to the hydraulic system of the road paver and also to the actuators of the extension screeds, so that the hydraulic fluid of the hydraulic system of the road paver can flow through the lines up to the actuators of the hydraulic extension screed and back again. A connection to the hydraulic system of the road paver thus usually occurs in the prior art.
This is disadvantageous in that the connection to the hydraulic system of the road paver is complex and time-consuming. In addition, the repeated connection of different hydraulic lines of all attachment segments of a screed to the hydraulic system of the road paver leads to increased contamination of the hydraulic fluid of the road paver, which negatively affects the overall system. Furthermore, the laying of hydraulic lines through all segments of the screed, even those which do not require any hydraulic energy, leads to increased construction costs.
It is thus the object of the present invention to provide a solution for obtaining a variable paving width of a screed device of a road paver at the lowest possible manufacturing and reconfiguration costs. A solution shall further be provided for obtaining, if necessary, a variable width adjustment in a simple manner and without considerable modification efforts in road pavers which are exclusively equipped with rigid screeds, as are used, for example, for large paving widths.